The present invention relates to anchor nut-cage fixing systems for placing on a metal sheet from one of the faces of the latter with a view to receiving bolts presented from this same face, because of the inaccessibility of the other face due for example to the fact that the metal sheet forms part of a case, closed at least partially, as often happens in the bodywork of vehicles.
It relates more particularly, among said fixing systems, to those comprising:
a wing nut adapted for cooperating with an elongate hole formed in the metal sheet at the desired position,
and a holding and guiding cage adapted also to be mounted in this hole, which cage is formed by a moulded plastic material socket split longitudinally by windows through which the wings of the nut pass jointingly, said socket being connected to an external collar at one of its ends, and external bosses integrally moulded with this socket being provided for cooperating with the longitudinal ends of the hole for the purpose of angularly locking the socket after it has been axially introduced with the nut in this hole, and the socket nut assembly thus introduced has been moved through 90.degree..
Fixing systems of the kind in question, used for fixing on the metal sheet considered at least one piece disposed between the collar of the cage and the head of the bolt, generally give satisfaction.
But, for some uses, they have drawbacks.
One such use is when they are used for mounting an accessory on a vehicle body portion before application of the different paint and protection layers on the body portion.
In fact, the applications in question, which may be carried out when hot and which are generally followed by oven drying, have a number of consequences, in particular the following:
the plastic material collar is crushed, during the screwing providing the desired assembly, between the metal sheet and the piece fixed thereon; these two parts are then only separated from each other, in the vicinity of said collar, by a very small gap in which it is difficult for the often relatively thick paints to penetrate,
the end of said screwing, being limited by a reasonable degree of crushing of the collar, is not determined accurately,
there is a danger that the heating caused by the painting and/or drying operations damage the crushed collar to the extent that it modifies the clamping torque corresponding to the end of the above screwing and possibly cause slackening of the system.
In addition, the freedom of axial movement of the nut in the cage until it is clamped by screwing up the bolt may form a drawback in some applications, in particular when the screwing up is carried out upwards and/or when the nut is relatively flat and easily introduced into the cage through its windows.
An object of the invention, among others, is to overcome these different drawbacks.